Multibilayers

A study by Bames and co-workers of the equilibrium spreading behavior of dimyristol phosphatidylcholine (DMPC) reconciles the differences between spreading of bulk solids and dispersions of liposomes [41]. This study shows the formation of multibilayers below the monolayer at the air-water interface. An incipient phase separation, undetectable by microscopy, in DMPC-cholesterol... 

Gruszecki, W.I. and J. Sielewiesiuk. 1990. Orientation of xanthophylls in phosphatidylcholine multibilayers. Biochim. Biophys. Acta 1023 405 112. 

Kostecka-Gugala, A., D. Latowski, and K. Strzalka. 2003. Thermotropic phase behaviour of alpha-dipalm-itoylphosphatidylchohne multibilayers is influenced to various extents by carotenoids containing different structural features—evidence from differential scanning calorimetry. Biochim. Biophys. Acta 1609 193-202. 

Sujak, A., P. Mazurek, and W.I. Gruszecki. 2002. Xanthophyll pigments lutein and zeaxanthin in lipid multibilayers formed with dimyristoylphosphatidylcholine. J. Photochem. Photobiol. B Biol. 68 39 -4. 

Liposome Formation. The pioneering investigations of Bang-ham (5) have shown that thin films of natural phospholipids form bilayer assemblies if they are lyophilized in excess water by simple handshaking above the phase transition temperature. While this procedure results in the formation of large, multibilayered spherical structures, by ultrasonication of such lipid dispersions small unilamellar liposomes are formed (16), which are schematically shown in Figure 10. Additional metTiods for liposome preparation are described in a number of reviews (17,44,45,46). 

Micelles are spontaneously formed by most surfactants (especially single-chained ones) even at fairly low concentrations in water, whereas at higher surfactant concentrations, with or without the addition of an oil (e.g. octane) or co-surfactant (e.g. pentanol), a diverse range of structures can be formed. These various structures include micelles, multibilayers (liquid crystals), inverted micelles, emulsions (swollen micelles) and a range of microemulsions. In each case, the self-assembled structures are determined by the relative amounts of surfactant, hydrocarbon oil, co-surfactant (e.g. pentanol) and water, and the fundamental requirement that there be no molecular contact between hydrocarbon and water. 

Description of the different mimetic systems will be the starting point of the presentation (Sect. 2). Preparation and characterization of monolayers (Langmuir films), Langmuir-Blodgett (LB) films, self-assembled (SA) mono-layers and multilayers, aqueous micelles, reversed micelles, microemulsions, surfactant vesicles, polymerized vesicles, polymeric vesicles, tubules, rods and related SA structures, bilayer lipid membranes (BLMs), cast multibilayers, polymers, polymeric membranes, and other systems will be delineated in sufficient detail to enable the neophyte to utilize these systems. Ample references will be provided to primary and secondary sources. 

Controlled evaporation of SUVs and MLVs on substrates has been shown to result in the formation of ultrathin films which retained the regular bilayer structure of vesicles [69, 425-427]. These immobilized bilayers, termed as cast multibilayers , cast multibilayers , or ordered cast (ultrathin) films , have provided an alternative to LB films [425-446]. Alkylammonium surfactants with azobenzene (33) and glutamate (34) functionalities have been used, for example, in the preparation of cast-film-forming SUVs. X-ray diffraction... 

Cast multibilayers prepared from an azobenzene-containing surfactant (33) [426] and from mixtures of 33 and 5 display only short-term stabilities and low solubilities in water. These disadvantages have been overcome by coating the multibilayers with cellulose acetate and by using poly(vinyl alcohol) as a binder [429], The method of choice in preparing these composite cast multibilayers... 

Fig. 64. Plausible model of the molecular packing of the cast multibilayer of 34 as produced by electron-density matching of the X-ray diffraction data. The plane of the benzene ring is arbitrarily set in the plane of the two alkyl chains. When the benzene plane is assumed to be in the perpendicular disposition, the tilt angles for the spacer and tail chains become slightly greater 50° for the spacer and 75° for the tail [445]...

Fig. 65a, b. Photographs of cast multibilayer films a stiff 33 film b flexible 34 film [445]... 

Thin films have also been cast from fluorocarbon-surfactant-containing SUVs with bound poly(vinyl alcohol) [436, 437]. Wide angle X-ray diffraction measurements have been interpreted in terms of highly oriented multibilayers and complete substrate coverage by the fluorocarbon surfactants, even at low surfactant-to-poly(vinyl alcohol) ratios (Fig. 70) [437]. 

Composite cast multibilayers provided a route to the formation of multilayer, two-dimensional polymer networks [443, 445]. This method utilized the following steps (i) ultrasonic dispersal of 15 mM of the dialkylammonium surfactant, 35, and 15 mM of the bisacrylate monomer. 36 (ii) addition of... 

Fig. 67. Schematic representation of three types of anionic porphyrins in a cast multibilayer film of 34. The overall bilayer organization is assumed to be the same as that of Fig. 64. For clarity, counterions are not shown and the bilayer units are separated from each other. The spacer portion is also not shown in Stereogram . Type I porphyrins (Fig. 66) are inserted into the bilayer along the molecular axis of the spacer chain. Type II porphyrins are randomly placed on the bilayer surface. Type III porphyrins lie flat on the bilayer [445]...

A similar approach has been taken for preparing molecularly controlled siloxane networks [440,446]. Composite bilayer films were cast from mixtures of alkoxysilane (CH3Si(OCH3)3) and 37 or 38 on a fluorocarbon sheet and were kept at 25 °C and 60% relative humidity for three days. Exposure to gaseous ammonia in a closed vessel for ten days resulted in hydrolysis and subsequent condensation. The surfactants were then extracted by repeated immersion in methanol. Manipulation of the composition of the cast multibilayers allowed... 

Myoglobins [442] and iron-oxide particles [447] have also been organized in cast multibilayers. Flexibility and versatility render composite cast multibilayers to be suitable for the construction of functional, ultrathin, polymeric superstructures with molecularly defined morphologies. Cast-multibilayer... 

Cast multibilayers 2D,3D depends on substrate dimensions Controlled evaporation of surfactant deposited on substrates Weeks Viable alternative to LB films 427... 

Cast multibilayers prepared from cyclam-containing double-chain surfactants Size-quantized CdS particles generated in situ in cast bilayers... 

Cast multibilayers prepared from N-(co-(trimethyl-ammonio)undecanoyl) dioctadecyl-L-glutamate bromide dispersions Fe304 particles generated in situ Magnetic anisotropy of particles was retained in cast multibilayer films 797... 

Closed, onion-like, 1000- to 8000-A-diameter multibilayer aggregates, formed upon the swelling of thin surfactant (or lipid) films in water. 

Devaux et al. have described in some detail the use of the Bloch equations to relate electron spin-spin interactions between spin-labeled lipids to diffusion constants. This method was originally employed by Trauble and Sackmann,50 Scandella et al.,42 Devaux and McConnell,10 and Devaux et al.11 to measure diffusion constants in multibilayer model membranes and in biological membranes. In all cases diffusion constants of the order of those reported previously were obtained. 

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